Revealing electrochemically activated polymer infiltration into thick cathodes in solid-state batteries

Solid-state batteries are next-generation energy storage technologies that replace flammable electrolyte with safer solid counterparts. Yet, inorganic solid electrolytes suffer contact loss upon cathode volume changes during charge/discharge, limiting electrochemical performances. Polymer electrolytes are considered contact loss-free, especially when they are used above melting temperatures. We developed a new polymer that excels at room temperature. Interestingly, our preliminary results at ID31 beamline contest the common belief about polymers: it cannot infiltrate through the cathode under external mechanical pressure; yet the infiltration is strongly enhanced after the first charge/discharge cycle. Here we propose to use sub-µm X-ray CT at ID16B to resolve this puzzle, by finding out when and how polymer permeates in the electrode microstructure. The electrochemically activated infiltration mechanism may provide insights to design polymer electrolytes and solid-state batteries.